The present invention relates to a cell plate structure for a solid electrolyte fuel cell, a solid electrolyte fuel cell and a related manufacturing method thereof and, more particularly, to a cell plate structure for a solid electrolyte fuel cell, which uses a solid electrolyte to obtain electrical energy due to an electro-chemical reaction, a solid electrolyte fuel cell using such a cell plate structure and a related manufacturing method thereof.
In recent years, a great attention has heretofore been focused on fuel cells as clean energy sources that generate electric power output at a high energy conversion efficiency to be friendly in an earth environment.
Among these fuel cells, a solid oxide electrolyte type fuel cell (solid oxide fuel cell: hereinafter referred to as SOFC) employs electrolyte composed of an oxide ion conductivity type solid electrolyte such as yttria-stabilized zirconia.
In such an SOFC, it is proposed that both surfaces (front and rear surfaces) of the electrolyte layer are formed with porous electrodes to allow the solid electrolyte to serve as a partition wall wherein one electrode is supplied with fuel gas such as hydrogen or hydrocarbon and the other electrode is supplied with oxidizing gas such as air or oxygen to permit the fuel cell to generally operate at a temperature about 1000° C. for obtaining electrical energy.
Further, it is known that the solid electrolyte of such an SOFC has an electrical conductivity, lower than that of the electrolyte of a phosphoric acid type fuel cell or a molten carbonate type fuel cell approximately by one digit number. In general, electrical resistance of the electrolyte portion forms a loss in electric power generation output. In order to improve an electric power generating output density, it is important for the solid electrolyte to be formed in a thin film to have a film resistance with a value as low as possible. On the other hand, it is required for the electrolyte layer to have a surface area greater in value to some extent in order to enhance various functions of the fuel cell and, hence, the SOFC employs a cell structure (unit cell structure) wherein the electrolyte layer is formed on a supporting member having a mechanical strength.
Japanese Patent Application Laid-Open Publication No. H8-64216 discloses a fuel cell that attempts to form an electrolyte layer in a thin film and, more particularly, discloses a structure wherein a supporting substrate is formed with a large number of small opening portions each of which accommodates the cell plate structure structured to have a fuel electrode layer, an electrolyte layer and an air electrode layer deposited in three film layers, and a separator plate formed with flow passages, with the cell plate and the separator plate being alternately laminated. With such a structure, it is possible to use a non-porous silicon (Si) wafer as a supporting substrate which is formed with various elementary layers in film shapes, providing a capability of forming the electrolyte layer with a thickness in the order of approximately 2 μm. In particular, an electrolyte layer composed of stabilized zirconia formed in a single crystal film is formed on a Si substrate or a Si substrate formed with an oriented cerium oxide (CeO2) thereon.